/Engine/Plugins/Runtime/NetworkPrediction/Source/NetworkPrediction/Public/NetworkPredictionSerialization.h
This is the threshold at which we would wrap around and incorrectly assign a frame on the receiving side. E.g, If there are FRAME_ERROR_THRESHOLD frames that do not make it across from sender->receiver, the receiver will have incorrect local values. With 8 bits, this works out to be 128 frames or about 2 seconds at 60fps.
enum { FRAME_ERROR_THRESHOLD = MAX_FRAME_WRITE / 2 }